In theatrical makeup and camera-ready attire, her hair an ivory meringue, Diane Rehm is an intensely visual person — “I love clothes more than I love food,” she likes to say — whose medium happens to be radio.

Her voice sounds ancient and fragile, as though dragged through shattered glass and gravel. She was diagnosed almost two decades ago with spasmodic dysphonia, a neurological disorder that causes spasms of the vocal cords and should have axed her career. Instead, it helped distinguish her from the dulcet chorus of NPR voices. “The Diane Rehm Show,” which airs locally from 10 a.m. to noon, is heard weekly by 2.4 million listeners on nearly 200 stations.

She is dramatic in a job that demands restraint, given to maestro-level gestures lost on listeners. “I’ve been an actress all my life,” she declaims. A wren of a woman with an XXL personality, she’s known for a hailstorm of 0pinions.

“She’s very challenging. We had our first fight before I even got here,” says J.J. Yore, manager of WAMU-FM (88.5), a Washington NPR affiliate. Earlier this month, before she took a sabbatical for her thrice-yearly voice treatments, they had an hour-long dustup. Says her dear friend Mary Beth Busby, “You don’t ever ask Diane’s opinion if you don’t want it, because you’re going to get it.” Yet Rehm is celebrated for moderating civil discourse between often vehemently opposed guests.

Now 79, the most unretiring Rehm announced last month that she plans to leave the show, not retiring, exactly, but “stepping away from the microphone.” Mind you, this will happen almost a year from now, Dec. 31, giving her time for an extended victory lap.

But she’s ready for her next act. She doesn’t plan to fade away. Among other things, she will raise funds for the station. In 1995, she raised $250,000 to take her show national.

John and Diane Rehm on the publication of their 2002 joint memoir, "Toward Commitment: A Dialogue About Marriage." John Rehm ended his life in June 2014 after years with Parkinson’s disease. (Lucian Perkins/The Washington Post)

Most likely, she will become more outspoken. Her new memoir, “On My Own,” recounts her husband’s decision to end his life in June 2014 after his physician was legally barred from helping. John Rehm was diagnosed with Parkinson’s disease in 2005, and after two years in an assisted living facility, he refused food, liquids and medication.

It took 10 days for him to die, an eternity.

“I rage at a system that would not allow John to be helped toward his own death,” Rehm writes of watching her spouse of 54 years wither away.

The experience sparked her advocacy in the right-to-die movement. “I feel the way that John had to die was just totally inexcusable,” she told The Washington Post last year. “It was not right.”

Her public stand, and a commitment to host three dinners for the organization Compassion & Choices, which advocates for legalizing physician-assisted suicide, resulted in an admonishment from a room full of station and NPR brass. Rehm is supposed to moderate news issues, not make them.

“I was annoyed,” Rehm recalls of the experience. “Political issue or not, it’s also an extraordinarily personal one to me because of John.”

In June, Rehm landed in trouble again. On air, she said to Sen. Bernie Sanders, “You have dual citizenship with Israel,” which he does not. The source was a Facebook posting, part of an Internet conspiracy reportedly leveled at Jewish legislators.

“Worst mistake of my career,” Rehm says, slapping her thigh. “I took full responsibility for that. I should have checked and checked and checked.” She felt, she says, “terrible, terrible. Worst of all to have insulted that man, because he is such a decent man.”

So, not an easy year. She had already discussed leaving the show. She turns 80 in September, a good time for change, an end to 5 a.m. wake-ups, but she opted to work through the election.

“It’s time for me to retire, especially on the issue of right-to-die, to be able to speak out and to speak freely,” she says, sitting in her crescent-shaped office in upper Northwest, which is filled with family photos, honors and an image of Mr. Rogers. (“I. Just. Loved. That. Man.”) Her limping, long-haired chihuahua, Maxie, 12, naps at her high-heeled feet.

Like her owner, Maxie is tiny but fierce. Unlike her owner, Maxie is also an accomplished biter who loves few others. Rehm tends toward unbridled enthusiasm, routinely embracing guests.

Her life is an open book. Actually, several books. If listeners feel that they know Rehm, a mother of two and grandmother of four, that’s because she has shared plenty.

“Finding My Voice” is the 1999 account of her improbable career, rising from volunteer on a home show to radio dominance. She grew up in Washington’s Petworth neighborhood, the daughter of Christian Turkish and Egyptian immigrants. Her family owned a food market at 19th and Wyoming. There was no money for college, no discussion either. “I had no ambition other than to be a good secretary,” she says. She learned to type 120 words per minute in courses at Roosevelt High School.

“Toward Commitment: A Dialogue About Marriage” is a frank, moving 2002 memoir written with John Rehm, an attorney she first met while working as a secretary at the State Department. (She invariably refers to her late husband by his full name or by Scoop, his childhood nickname.) There’s even a book about Maxie. (We did not read that one. Maxie is not an amiable beast.)

Rehm finds privacy overrated. “Commitment” recalls both Rehms being attracted to other people, though not acting on it. “On My Own” writes of John’s “deliberately emotional abusive behavior,” executed through silence and withdrawal that could last a month at a time. Does she regret sharing so much?

“There ain’t no perfect marriages in this world, but people pretend. John and I were determined not to pretend,” she says. “I think that in writing that book, it was the most profound experience next to his dying that we could have had.”

Knopf editor Robert Gottlieb once told her, “You have to be mindful of how much you want to expose. How much do you want the public to know about you?”

The night after he said that, she dreamed she was whitewashing the walls. She has held back little since.

President Obama awards the National Humanities Medal to Rehm in 2014. (Charles Dharapak/Associated Press)

Some things to know about Rehm: No, it doesn’t hurt to talk. Yes, everyone asks her this. If she likes something she’s said, she’s prone to uttering it twice.

Show topics she avoids: Shakespeare, physics. Also, abortion and gun control, though she recently did one on the latter. “It’s like butting heads!” she says. “We’re not making progress!” Favorite guests: Margaret Atwood, Mandy Patinkin, Julie Andrews, Hillary Clinton.

She doesn’t eat much, and rarely lunch, and dropped 25 pounds when John was dying. Every evening, whether she’s out or in her 14th-floor apartment in Glover Park, she enjoys two glasses of champagne. Nothing pricey, Korbel Brut. “Champagne doesn’t put pounds on me,” she says. “Food puts pounds on me.” On the weekends, she wears casual clothes. (Well, she claims she does. There is no evidence of this.)

In 2014, she was awarded the National Humanities Medal. When President Obama put the crimson ribbon around her neck, she asked when he was coming back on the show.

She has astounding recall; she’s able to name many of the women on her State Department softball team of nearly 60 years ago. She played second base. “I was such a good athlete!”

She drives a 2002 Toyota Avalon, “which I hope to drive for the rest of my life.” She’d rather spend her money on clothes.

She doesn’t read the books for her show. That’s left to her dedicated, all-female staff of producers, five full-time and three part-time. “They give me really, really first-rate notes,” included in detailed scripts, she says.

“She’s a demanding boss in a really good way,” says producer Sandra Pinkard, who has been with Rehm since 1993. “The show’s a democracy, with one person’s vote counting a whole lot more” than everyone else’s. Guests are pre-screened and interviewed to weed out the duds. Says Rehm, “They might be good writers, but not good talkers.” Occasionally, a dud squeaks through. She was none-too-pleased when former Maryland governor and presidential candidate Martin O’Malley missed a September studio interview and excoriated him on the air. Or in 2007, when Newt Gingrich left a phone interview 40 minutes into a planned full hour. Rehm chewed him out, too.

She is intensely social and goes out constantly. Says Busby, “If you called 20 different women in this town, every one would say, ‘Diane is my very best friend.’ I’m one of them. People confide in her. They know they won’t be judged.”

She won’t marry again. She has had her true love. Close to her two children — Jennifer is an internist outside Boston, David is provost of Mount St. Mary’s University in Maryland — she likes living on her own. “I don’t have to ask or check with somebody else about what I’m going to do or where I’m going,” she says, leaning forward and stressing every word. “It’s the first time in my whole life I have lived alone. And I’m fine with it! I’m fine with it! There is freedom. There is choice. There is security.”

Rehm in the Oval Office with President Bill Clinton in 1998. (WAMU American University)

The program is called “The Diane Rehm Show.” For WAMU, the transition won’t be easy. “She represents huge stature for the station, our face to the world, not just to the city,” says Yore, who has a list of about 35 candidates to replace her on the next incarnation of the program.

“The last thing I would ever want to do is manage a transition with a revered, iconic figure in a way that doesn’t honor everything she has done and contributed and all that she represents,” says Yore, who suggested that Rehm try fundraising, along with a couple of dozen other ideas. In developing the station’s next chapter, Yore says, “I see her as a really important partner.”

“I plan to work for the station forever,” she says, initially working three times a week raising money and helping in other ways. “I don’t want ever to retire from everything, and to work as long as I am able.”

After she stops hosting the show, Rehm plans to speak out on Parkinson’s, Alzheimer’s and the right to die.

When her time comes, if there is no physician-assisted way to end her life, she will do exactly the same as John did.

“If I can no longer do what I physically want to do, I’m out of here!” she says. “Death is not something I feel frightened of.”

Leaning over in her sunny office, as if sharing a big secret, as if she has secrets, she says in a near whisper, “You know, I’ve had a great life! Great!”

Diane Rehm book launch events WAMU will host a book party Tuesday at the Newseum, $60 per ticket, registration required. Rehm will also talk about the memoir March 2 at Sixth & I, tickets and $20 minimum registration.